Physiological electrodes attached to the skin of a subject can receive electrical signals generated by the human body, which are then used to monitor physiological functions (such as heart rate and muscle activity), and/or can deliver electrical signals to the body, for example to stimulate muscle contraction or relieve pain.
For example, transcutaneous electrical nerve stimulation (TENS) is a technique in which electric current is applied to a body part of the subject via two or more skin mounted electrodes. TENS treatment typically requires electrical current to be applied to the body for a significant amount of time each day, including while the subject goes about their daily activities. In wireless TENS, a TENS device (which generates the electrical current) is placed directly on an electrode attached to the skin of a subject. FIG. 1 shows a wireless TENS system comprising a TENS device 10, two electrodes 12, 14 and a remote control 16 being used to treat the lower back of a subject 18. It is preferable for the TENS device to be very limited in size to prevent hindering of movement and to ensure comfort when worn under clothing. Construction height of TENS devices is therefore a very important factor, which is significantly influenced by the type of connector used to connect the TENS device to the electrode.
Additionally, it is a key benefit for the TENS user to be able to easily connect and disconnect the TENS device from the electrode, thus facilitating placement of the device on electrodes in difficult to reach body positions (e.g. the back). An easy-to-use connector is also necessary for subjects who have reduced use of their hands and fingers (for example because they suffer from osteoarthritis).
Known skin electrodes, including those used for TENS, are typically connected to a medical device (such as a TENS device) using a mechanical connection. For example, a typical electrode has a male snap structure configured to engage in a snap-fit connection with a female receiving portion of the medical device connector. As such, force is required to connect and disconnect the electrodes from the medical device connector. This makes such connectors difficult to use by people who are unable to easily apply the required amount of force. It also makes connection to electrodes located on soft body parts (such as the stomach) very difficult or impossible, since such body parts do not provide a firm support to press against. It also makes connection to electrodes located on painful body parts (for example which have been injured) unpleasant; since the force which needs to be applied may cause further pain and discomfort.
These difficulties of connecting the medical device connector and the electrode may lead to improper connections, reducing the effectiveness of the treatment or monitoring being carried out by means of the medical device.
To mitigate these issues, the use of magnetic connectors to connect medical devices to electrodes has been proposed. WO2011/151742, for example, describes an electrode assembly comprising an electrode and a connector, in which a connection between the electrode and connector is formed by way of a magnet provided in the connector assembly magnetically coupling to a magnet or magnetized material in the electrode.
U.S. Pat. No. 4,112,941 A discloses a connector assembly with a connector containing a magnet and a hole for mating with an elongated upstanding contact member of an electrode. An additional clearance is provided in the hole to allow for an unhindered intentional disconnection of the connector from the electrode.
KR 2011 0120483 discloses a terminal connection module comprising a first connection body with a magnetic part and a second connection body with a corresponding magnetic part that is connectable to the first magnetic part. When connected, terminal parts in the first and second body electrically contact each other.
US 2011/171837 shows a connector system with a plurality of magnetic elements arranged around a first and a second cable, respectively. Furthermore, at least one guiding element may be configured to orient the cables correctly.